5121835-TIM-J-1118
Johnson Controls Ducted Systems
47
2.
Using the hole drilled in step 1, insert eight inches of 1/4
inch metal tubing into the airflow of the return and supply
air ducts of the unit.
Note:
You must insert the tubes and hold them in a position
perpendicular to the air flow so that velocity pressure
does not affect the static pressure readings.
3.
Use an inclined manometer or Magnehelic® to determine
the pressure drop across the unit. This is the external static
pressure (ESP). In order to obtain an accurate
measurement, verify that the air filters are clean.
4.
Determine the number of turns the variable motor sheave
is open.
5.
Select the correct blower performance table for the unit
from Table 18. Tables are presented for side and bottom
duct configuration.
6.
Determine the unit measured CFM from the blower
performance table, external static pressure, and the
number of turns the variable motor sheave is open.
7.
To adjust measured CFM to required CFM, see
8.
After you note the reading, remove the tubes and seal the
holes.
9.
Tighten the blower pulley and motor sheave set screws
after any adjustments. Re-check the set screws after 10-12
hours run time.
Note:
You must repeat this procedure with the addition of
field-installed accessories.
Figure 30: Dry coil delta P
Failure to properly adjust the total system air quantity
can result in extensive blower damage.
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500
Air Flow Rate (cfm)
Coil Pressure Drop (iwg)
100% Return Economizer
No Economizer
ZKT06
ZKT07
ZKT08
ZKT10
ZKT12
